arm64: efi: ignore EFI_MEMORY_XP attribute if RP and/or WP are set

The UEFI memory map

is a bit vague about how to interpret the
EFI_MEMORY_XP attribute when it is combined with EFI_MEMORY_RP and/or EFI_MEMORY_WP, which have retroactively been redefined as cacheability attributes rather than permission attributes.

So let's ignore EFI_MEMORY_XP if _RP and/or _WP are also set. In this case, it is likely that they are being used to describe the capability of the region (i.e., whether it has the controls to reconfigure it as non-executable) rather than the nature of the contents of the region (i.e., whether it contains data that we will never attempt to execute)

Cc Stephen Boyd <[email protected]>

Cc Matt Fleming <[email protected]>

Signed-off-by Ard Biesheuvel <[email protected]>

---
 arch/arm64/kernel/efi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

arch/arm64/kernel/efi.c +3 -2

index 82cd07592519..f85ac58d08a3 100644
@@ -48,7 +48,9 @@ static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
                return pgprot_val(PAGE_KERNEL_ROX);
 
        /* RW- */
-       if (attr & EFI_MEMORY_XP || type != EFI_RUNTIME_SERVICES_CODE)
+       if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
+            EFI_MEMORY_XP) ||
+           type != EFI_RUNTIME_SERVICES_CODE)
                return pgprot_val(PAGE_KERNEL);
 
        /* RWX */
--

2.11.0

The UEFI memory map is a bit vague about how to interpret the EFI_MEMORY_XP attribute when it is combined with EFI_MEMORY_RP and/or EFI_MEMORY_WP, which have retroactively been redefined as cacheability attributes rather than permission attributes.

So let's ignore EFI_MEMORY_XP if _RP and/or _WP are also set. In this case, it is likely that they are being used to describe the capability of the region (i.e., whether it has the controls to reconfigure it as non-executable) rather than the nature of the contents of the region (i.e., whether it contains data that we will never attempt to execute)

Cc Stephen Boyd <[email protected]>

Quoted 11 lines · Ard Biesheuvel

The UEFI memory map is a bit vague about how to interpret the EFI_MEMORY_XP attribute when it is combined with EFI_MEMORY_RP and/or EFI_MEMORY_WP, which have retroactively been redefined as cacheability attributes rather than permission attributes.

So let's ignore EFI_MEMORY_XP if _RP and/or _WP are also set. In this case, it is likely that they are being used to describe the capability of the region (i.e., whether it has the controls to reconfigure it as non-executable) rather than the nature of the contents of the region (i.e., whether it contains data that we will never attempt to execute)

Quoted 1 line

Cc Stephen Boyd <[email protected]>

Reported-by Stephen Boyd <[email protected]>

I will test early next week and provide a tested-by. Thanks.

Quoted 12 lines · Stephen Boyd

Quoted 11 lines · Ard Biesheuvel

The UEFI memory map is a bit vague about how to interpret the EFI_MEMORY_XP attribute when it is combined with EFI_MEMORY_RP and/or EFI_MEMORY_WP, which have retroactively been redefined as cacheability attributes rather than permission attributes.

So let's ignore EFI_MEMORY_XP if _RP and/or _WP are also set. In this case, it is likely that they are being used to describe the capability of the region (i.e., whether it has the controls to reconfigure it as non-executable) rather than the nature of the contents of the region (i.e., whether it contains data that we will never attempt to execute)

Quoted 6 lines

Quoted 1 line

Cc Stephen Boyd <[email protected]>

Reported-by Stephen Boyd <[email protected]>

I will test early next week and provide a tested-by. Thanks.

Great, thanks.